Let he bought 2x marbles. 27 marbles costs = Rs.2M so 1 marble costs = Rs.2M/27 Therefore, x marbles costs = Rs. (2M × x) / 27 Now we calculate the selling prices. He sold x marbles at the rate of 13 for Rs.M so 1 marble selling price = M/13 x marbles selling price = x × M/13. He sold another x marbles at the rate of 14 for Rs.M so 1 marble selling price = M/14 x marbles selling price = x × M/14 Now, 2Mx/27, xM/13, xM/14 are integers. So x marbles must be divisible by 27, 13, 14 i.e LCM of 4914 So, 2x = 9828.